The long term objective of this research is to further our understanding of the molecular mechanisms of fertilization, preimplantation embryo development , and implantation. Such studies are critical for the advancement of two clinically important areas: infertility and contraceptive development. To this end, we are using the mouse as a model system to study the reproductive biology that underlies these processes. We have recently identified on the surface of mouse eggs, embryos, and uterine epithelium, a novel tetraspanin protein called epithelial membrane protein 2 (EMP2). Tetraspanin proteins interact with cell surface integrins, and are emerging as critical regulators of many cellular processes, including cell adhesion, proliferation, and differentiation. EMP2 is known to interact with intergrin beta1, an intergrin thought to be critical for fertilization and possibly involved in implantation. The surface localization of EMP2, as well as known roles of previously identified tetraspanins, suggest a function for EMP2 in cellular interactions important for these early processes of reproduction. The first aim of this proposal is to characterize the expression pattern of EMP2 mRNA and protein in oocytes, embryos, and uterine tissue. This will be done using RT-PCR, immunofluorescence, and immunoblotting techniques. The second aim is to determine if inhibition of EMP2 expression and/or function results in inhibition of fertilization, preimplantation embryo development, or implantation. This will be done using both dominant negative and RNA interference approaches. In addition to improving our understanding of molecules relevant for the signal transduction pathways important in early reproduction, results of these studies may also have implications for clinical practice of assisted reproduction, as well as contraceptive development.